Postoperative period: patients will receive acetaminophen 1000mg q6 hourly, celexocib 200mg q12 hourly and gabapentin 200mg q8 hourly given orally. Patients will also receive hydromorphone contin 3mg q8 hourly and a hydromorphone patient controlled analgesia (PCA) for breakthrough postoperative pain. Visual analogue scale (VAS) will be assessed 4 hourly for the first 48 hours. Total hydromorphone consumption and time of first PCA dose will be recorded. The patient will be given a 24 h diary to record VAS on. The research assistant will interview the patient on postoperative day one and two. VAS scores will be documented from the patient diary and the nursing records.